Alkylation of isoparaffins with olefins



Patented Apr. 30,1946

OFFICE {\LKYLATION OF ISOPARAFFINS WITH OLEFINS Sumner H.McAllistenLafayet'te, and John Anderson and William E. Ross, Berkeley,Calif., assignors to Shell Development Company, San Francisco, Calif., acorporation of Delaware No Drawing. Application January 29, 1942, SerialNo. 428,676

This invention relates to the alkylation of paraflin compounds,particularly parafiins having a tertiary carbon atom, by reaction withan olefin in the presence of acid alkylation catalysts. It deals with amore advantageous alkylation process whereby the quality of the productsmay be improved and operating costs may be materially reduced,particularly when using normally liquid olefins as the alkylating agent.

One of the principal items of expense in the manufacture of alkylationproducts by reaction of isoparaflin compounds with olefins in thepresence of acid catalysts, such as sulfuric, chlorosulfonic,hydrofiuoroboric, hydrofluoric, and like acids, is the cost of catalystacid which is high because of the relatively short effective life ofsuch catalysts under the usual conditions of reaction, especially withnormally liquid olefins. The deterioration or decline in alkylatingability of catalyst acids is usually associated with the formation ofundesirable products, particularly higher boiling products, which reducethe yield and quality, of the desired alkylation product. While theexact mechanism of the changes responsible for the loss of activity ofacid alkylation catalysts is not fully understood and possibly involvesboth dilution and poisoning effects, a method has been developed whichlargely overcomes the diiflculties formerly associated with suchcatalyst deterioration.

The process of the invention is based upon the discovery that treatmentof the reactants, before contacting them with the alkylationcatalyst-acid, under conditions adapted to destroy and/or removecompounds more reactive than the olefin or olefins to be used in thealkylation, is capable of materially increasing the efiective life ofthe catalyst acid. In copending application Serial No. 281,882, filedJune 29, 1939, the improvement of the life of alkylation catalyst acidsby removal of diolefins and acetylenic compounds from the feed stock isdescribed and claimed. Among the methods there disclosed for effectingsuch removal are polymerization treatments with sulfuric acid, forexample, sulfuric acid which has been usedin the alkylation step of theprocess. The present invention deals with an improved method forcarrying out alkylation procedures of this general type.

It has now been found that in alkylating isoparafilns and the like withnormally liquid olefins unexpected advantages may be obtained bypretreating the olefinic feed stocks with acid under certain carefullycontrolled conditions. More particularly, it has been discovered that bytreatment of the olefinic feed stocks so as to remove along withimpurities such as diolefins a small regulated amount of themono-olefin, not only a material increase in the alkylation" catalystlife but also an increase in the yield of alkylation products boiling inthe gasoline range as well as in the yield of total alkylation productsmay be obtained. Specifically, it has been found that improvedalkylation results are best obtained by treating amylenes or higherboiling olefins with acid under controlled conditions, contacting thetreated-hydrocarbons with a base and then distilling the treatedhydrocarbons to remove the polymer produced in the pretreatmentoperations. This method of operation has special advantages over prioralkylation procedures. It gives very much improved catalyst lifecompared to methods of alkylation in which the polymers are permitted toenter the alkylation stage of the process since, as will be more fullyshown hereinafter, the polymers are quite detrimental to alkylation acidcatalyst life. The new procedure also gives much higher yieldsof usefulalkylation products than can be obtained by theuse of previouspolymerization methods prior to alkylation since such methods, incontrast to the ,invention remove large amounts of monoolefin from thealkylation feed stock. Thus, the process of the invention gives improvedresults based both on the amount of catalyst and of olefin used. Stillanother important advantage of the process is that by its use theeffective life of not only the alkylation acid but also the pretreatingacid is extended so that a small amount of pretreating acid only isrequired and I the whole process is made more economical. This isaccomplished by carrying out the pretreatment under conditions at whichthe contamination of the pretreating acid is minimized.

The process of the invention may be applied to the reaction of saturatedaliphatic compounds having a hydrogen atom attached to. a tertiarycarbon atom with normally liquid olefins regardless of the source ormethod of preparation of the reactants. Saturated compounds which may bereacted in accordance with the invention include, for example, 2-methylpropane, 2- methyl butane, 2- and 3-methyl pentanes 2,3- and2,4-dimethyl pentanes, 2,2,4-trimethyl pentane, 3-ethyi pentane, methylcyclopentane and higher homologues and suitable substitution productssuch, for example, as halogenated paraflins and the like. Compoundswhich may be reacted with such saturated compounds include olefins such'as alpha and beta amylenes,

isopropyl ethylene, trimethyl ethylene, unsymmetrical methylethylethylene, hexylenes including isoand tertiary-butyl ethylenes, theheptylenes, normal and iso-octylenes, cyclopentene, cyclohexene andanalogous higher oleflns.

Particularly advantageous sources of isoparaflins and olefins which maybe used are, for example, hydrocarbons derived from petroleum products,

shale oil, coal, peat, animal and vegetable oils,

and like carbo'niferous materials. The isoparamns and/or olefins presentin the startin material may be of natural occurrence or the result ofsuitable treatment of the parent hydrocarbon. Thus, for example, theisoparafflns may be obtained by isomerization, rearrangement, catalyticreforming or like treatment of normal or less branched chain paraflins,or by suitable treatment, with or without catalysts, of higher boilingmaterials which may or may not contain isoparafiin, or by hydrogenationof olefin polymers,

or by other suitable methods. The oleflns used the presence ofconcentrated sulfuric acid will be emphasized in the detaileddescription of its method of execution. V

In the first step in the new process the olefincontaining hydrocarbon iscontacted with a polymerlzation catalyst, for example, a-stronginorganic acid as sulfuric or phosphoric acid or the like, underconditions controlled so as to convert only a small. regulated amount ofthe mono-oleflns present; most preferably not more than about 5% byweight of the mono-oleflns are polymerized. The conditions to be used inthis treatment will depend upon the nature of the hydrocarbons presentand the character of the polymerization agent chosen. For the treatmentof pentane-amylene fractions of cracked petroleum products, for example,the followin conditions have been found to be advantageous when usingsulfuric acid as the treating agent:

Contact time, about 1 to 5 minutes, preferably 2 to 3 minutes.

Reaction temperature, about 30 C. to 50 C.,

preferably 35 C. to 40 C.

Acid concentration, 55% to 70% by weight, preferably 65% by weight. Acidto hydrocarbon volume ratio, at least 0.5:1,

preferably 12:1.

These reaction variables are interdependent so that analogous resultsmay be obtained outside the preferred ranges by making suitableadjustments in the other conditions. Thus, for example, an increase inthe acid concentration may be compensated for by decreasing the. contacttime or reaction temperature, or both. with more active polymerizingagents such as aluminum chloride and the like, it is desirable to employlower temperatures and smaller amounts of treating agents, although thecontact time may also be reduced. particularly where vapor phasetreating methods are employed. When using less active polymerizationagents such, for example, as phosphoric acid or benzene sulfonic acid orantimony trichloride, etc., it is advantageous to use highertemperatures and/or longer contact times to compensate for the loweractivity of the treating agent. In treating hydrocarbon fractionscontaining less active olefins, it is also desirable to somewhatincrease the rigor of the treatment. Thus, for example, for thetreatment of cracked gasoline of 70 C. end point with an equal volume of65% sulfuric acid a contact time of 6 to 15 minutes at a reactiontemperature of 40 C. to 50 C. is preferred. I

Any suitable method of contacting the polymerization agent andolefin-containing hydrocarbon may be employed. For, example, the tworeactants in the liquid state may be agitated in a mixing device orsubjected to concurrent or countercurrent flow in a packed tower or thelike. U. S. Patent 2,232,674 describes a method for carrying outreactions which may advantageously be adapted to the first step of thepresent process. Solid polymerization catalysts suspended in theolefin-containing hydrocarbon may be used in the same way as liquidpolymerization agents. Alternatively, the olefin-containing hydrocarbonmay be passed in the vapor phase over the catalyst in solid form, usingreduced pressure if desired.

After the acid treatment the separated olefincontaining hydrocarbon ispreferably treated with a base to neutralize any acid component presenttherein. This may be accomplished by scrubbing with a preferably dilutesolution of caustic soda or ammonia or lime or .the like, or byhydrolyzing at about C.- C. with such a solution, preferably underconditions at which intimate contact of the hydrocarbon and a basicagent is promoted. Instead of carrying out the neutralization as aseparate step in the process, it may be effected during the distillationstage as by injecting a 3% caustic soda solution, for example, into thefractionation column used for separating polymerization products fromthe treated olefins. Whatever method of neutralization or hydrolysis isadopted, the treating agent may be recirculated to the treating unitafter separation from the hydrocarbon, the desired concentration or basebeing maintained by either batch replacement of spent treating solutionor continuous or intermittent partial replacement thereof with freshbase. In some cases it is desirable to water-wash the acidtreatedhydrocarbon before contacting it with the base in order to preventemulsiiication difiiculties during the neutralization.

The higher boiling products formed by the treatment of theoleflnecontaining hydrocarbon are removed prior to contacting the olefinwith the alkylation catalyst. Any suitable fractionation method may beused, flash distillation being generally advantageous. The point atwhich the separation should be effected will depend upon the oleflnsinvolved and the conditions of pretreatment used. As a rule it ispreferred to distil to about the same end point as that of the startingmaterial, but in some cases it is possible to use higher distillationtemperatures at which a part of the lighter reaction oducts. not higherboiling than dimers of the starting olefin, are included with thelatter. The higher boiling hydrocarbons separa ed in the distillationare not a loss in the process but are high octane materials which aresuitable for use in motor fuel. They are .undesirable components of thealkylation feed, however, it having been found that olefin-containinghydrocarbon which had been acid-treated and waterand causticwashed gaveonly a small improvement in alkylation compared with the samehydrocarbon which had been redistilled after similar treatment.

Any suitable method of reacting parafilns with olefins and the like inthe presence of acid alkylation catalysts may be used in the alkylationstep of the process. The alkylation may be carried out with either orboth reactants in the vapor phase, but liquid phase reaction ispreferred. Any suitable method of intimately mixing the reactants andcatalyst acid may be employed. For example, jet mixers, towers providedwith suitable bafiles or packing, power-driven mixers and the like maybe used. For large scale, continuous operation mixing by means of a pumpwhich is in communication with a separator wherein reaction products maybe separated at least in part from catalyst acid and the latter returnedto the reaction, preferably together with a part of the separatedproduct-containing phase to which fresh reactants are added before beingcontacted with catalyst acid, is advantageous. A preferred a method ofoperation which is more fully described and claimed in copendingapplication of Sumner H. McAllister, Serial No. 245,714, filed December14, 1939, comprises circulation of a stream of.reacted mixturecontaining unreacted isoparafiin and continuously feeding into themixture isoparafiin and olefin to be reacted therewith, the formerpreferably in molecular excess, while taking oil from the circulatingemulsion reacted mixture from which product equivalent to the feed iswithdrawn and the remainder returned to the system. Preferably amolecular excess of isoparailin over olefin is used in the reaction andmost preferably the pretreated olefin is mixed with a molecular excessof isoparaffin before it is contacted with catalyst acid.

The conditions of alkylation which will be most desirable in anyparticular case will depend upon the nature of the isoparaifin andolefin involved.

Where sulfuric acid is employed as the catalyst,

initial concentrations of about 90% to 100% may be used although fumingH2804 is also suitable provided lower reaction temperatures are used.Temperatures of the order of about 5 C. to 50 C. may be used. Theproportion of catalyst to hydrocarbon which will be desirable willdepend upon the olefin being reacted. In general, volume ratios of about.5210 to about 4:1 are suitable. Reaction times of about five tothirty-five minutes are preferred but may be varied depending upon thetype of apparatus and method of operation from a fraction of a minute toas much as 60 minutes. Most preferably molar ratios of isoparamn toolefin of at least 20:1 are used in the reaction mixture in order. tofavor-alkylation and to suppress undesirable reactions such as olefinpolymerization, and it is usually advantageous to use ratios of theorder of 50:1 to 500:1 at the point where the olefin first contacts theacid. While the same ratio of paraflin to olefin may be used in the feedas is employed in the reaction, when the preferred method of feedingreaction mixture into recirculated reaction product is used, ratios ofisoparaflin to olefin of about 3:1 to 20:1 in the feed are preferred.Single or multiple stage alkylation with either concurrent or countercurrent flow of reactants and catalyst may be contained 0.019% totalsulfur.

' 0 used with either batchwise, intermittent or continuous operation. Y

The following examples illustrate the advantages of the process of theinvention and show how it maybe carried out:

EXAMPLE I An amylene-pentane fraction from Dubbs cracked gasoline wasused as olefinic feed for the alkylation of isobutane. Theamylene-pentane fraction had an end point of 50 C., a diene number of 28(mg. maleic anhydride per 100 ml. of hydrocarbon), a bromine number of121, and

The amylenepentane fraction was pretreated with sulfuric acid in abronze rotary-type mixer connected to a separator from which an acidreturn line led back to the mixer. The mixer and separator were firstcharged with the requisite amount of acid, the valve in the acid returnline being closed. The mixer was then filled with amylene-pentane andstarted. After the initial charge had received sumclent contact, theremainder of the amylene-pentane was forced into the mixer at the properrate and the acid return valve was opened suiilciently to keep the acidat the proper level in the separator. The pumping action of the mixercarried the acid and hydrocarbon mixture to the separator. pentane wasrun from the separator into. an accumulator from which it was withdrawnfor washing, neutralization or distillation, etc., prior to use inalkylation as described below.

The alkylation was carried out in an identical eter to measure thevolume of the added hydrocarbon. The hydrocarbon phase from theseparator was bled ofi through a regulating valve into a strippingcolumn, from which crude alkylate was obtained as bottoms. Thestabilized alkylate was refractlonated to separate an aviation gasolinecut, the octane number of which was determined. r.

Pretreatment Acid concentration.-..percent. None 63 03 65 05 Contacttime "minutes. None 0-7 6-7 0-7 6-7 Temperature Nmlil 10 1o 40 40 Acidto hydrocarbon volume ratioinmlxer None III III l/l l/l End point afterredistlllation 40 4 (0 Lbs. amylene-ientane treated wper lb. of aci None9.7 9.7 10510.0 t. percent amylene-pentano recovered 95.5 95.5 100 100Wt. percent am lane-pentane absorbed byacd ca.3.0 ca. 3.0 1.0 1.0' Wt.B67061}! polymers produced be ing above 50 C 4-5 4-5 9-10 9 Percent H 80in acid phaso after treatment 47. 0 47.0 59.5 00.3 Alkylat'ion Wt. percent amylene-pentane 'inieed 16.3 16.5 16.5 16.9 16.9 Wt. percentisobutanelnfeed. 72.3 72.8 73.4 77.5 77.5 Wt. percent normal butane infeed 11.4 10.7 10.1 5.0 5.6 5 Wt. Eercent yield of total alky te 137 136180 144 137 Average wt. percent of 15l50 0. cut alkylate at 85percentalkylation acid acidity. 90.0- 92.2 04.0 94.0 02.0 Octane No. ofl5l50 C. out

of alkylate 84.0 84.5 85.0 36.0 85.5 Alkylat on acid life in volumes (0of aklylate or volume of alkglation so (1 at 85 percent sci ity 8.0 0.510.0 20.0 10.0

I Not distilled. Y Caustic washed but not distilled.

The treated amyleneacted without pretreatment.

hydrocarbon feed rate of 1.8-2.1 volumes per hour per volume of reactorspace, a contact time of 18-20 minutes in the reactor, and a temperatureof 10 C. The feed contained 10-11 mols of isobutane per mol of olefinand equal volumes of acid and hydrocarbon were maintained in thereactor. The results clearly show the improvements, particularly inalkylation acid life which may be obtained by pretreating olefinic feedstocks with acid, neutralizing and distilling prior to use of theolefins in alkylation.

A particularly advantageous treating agent is spent alkylation acid.Using such acid diluted to 65.5% and extracted with butane, we haveobtained results equal to those secured with fresh acid.

Using the same apparatus as employed for the tests of Example I, acracked gasoline of 70 C. end point was used for-alkylation ofisobutane. The gasoline consisted of about 60% by weight of hydrocarbonsof five carbon atoms per molecule and 40% by weight of hydrocarbonshaving six carbon atoms per molecule. The bromine number of the gasolinewas 128.5 indicating about 60% of olefins, while the diene number of17.2 indicated about '2% diolefins. This gasoline was treated at 40 C.with two volumes of sulfuric acid of 65% concentration per volume ofhydro: carbon using an average contact time of 6-7 minutes, 8.9 poundsof hydrocarbon being treated per pound of acid used. The gasolineabsorbed by the acid was less than 0.5% and 96% of the gasoline wasrecovered. The treated gasoline was washed with sodium hydroxidesolution and then distilled to an end point of 80 C. to exclude thepolymers produced. Using a feed containing 18.5% t. the treatedgasoline, 75.7% of isobutane and 5.8% of normal butane and propane, thealkylation was carried out in the presence of a volume of sulfuric acidof 100% initial concentration equal to the volume of hydrocarbon in thereactor. A mol ratio of lsobutane to olefin of :1 was present in thefeed. The alkylation temperature was 10 C. and the contact time averaged20 minutes. The same gasoline was similarly re- The following are thecomparative results obtained:

1 Per cent Per cent Weight per cent yield of total alkylate. 125 143Avera weight or cent 0 il6"150 C.

cut in total 9.1 ylate at 85% slkylation acid acidity 82. 3 84. 8Overall yield of l50 C. cut-.. 103 110 Overall yield oi 40l50 C. out 77.6 81. 0 Alkylation acid life at 85% acidity---" 6. 0 14. 0

EXAMPLE III octane number of the depentanized alkylate of 126 C. endpoint was 92.5. An acid life of 20 volumes of product per volume of acidwas obtained compared to only 7 volumes when the same fraction was usedwithout pretreatment.

The life of the pretreating acid is quite long under the preferredoperating conditions. Thus, in large scale tests of the process the acidconsumption averaged only about one. pound of H1804 per barrel ofamylene-pentane fraction treated. It will be apparent, therefore, thatthe process offers many advantages over Prior alirylatlon methods. Theseadvantages may be realized under a wide variety of treating-conditionsusing widely diiferent acid treating agents, regardless of thealkylation method employed and the nature of the tertiary carbonatom-containing compound being alkylated or the liquid olefin or olefinsused as alkylating agent. It'will consequently be clear that theinvention is not limited to the details of operation disclosed by way ofillustration nor by any theory suggested in explanation of the greatlyimproved results obtained.

This application is a continuation-in-part of copendlng applicationSerial No; 281,882, filed June29, 1939.

We claim as our invention:

1. A process of producing higher boiling saturated hydrocarbons byalkylating isobutane with an amylene which comprises contacting an amyl-In plant scale tests of th process using amylene-pentane fraction ofhydrocarbon cracking products with sulfuric acid ofv 60% to 70%concentration at between about 30 C. and about 50 C. for 1 to 5 minuteswhile maintaining a volume ratio of acid to hydrocarbon in the reactionmixture of at least 0.5 to 1, intimately contacting the acid-treatedhydrocarbon with a. dilute sodium hydroxide solution, distilling theneutralized hydrocarbon to separate a fraction of substantially the sameend point as the original amylene-pentane fraction, and emulsifying theamylene content of the thus-separated fraction and isobutane withsulfuric acid of to concentration on a hydrocarbon-free basis whilemaintaining the ratio of isobutane to olefin at the point at which theolefin first contacts theacid between 50:1 and 500:1, whereby alkylationof the isobutane by said olefin is efiected and polymerization issuppressed.

2. A process of producing higher boiling saturated hydrocarbons byalkylating isobutane with a normally liquid olefin which comprisescontacting a mixture of hydrocarbon cracking products comprising saidolefin with sulfuric acid of 55% to 70% concentration at between 30 C.and 50 C. for 1 to 15 minutes while maintaining a volume ratio of acidto hydrocarbon of at least 0.5 to 1, neutralizing and distilling theacid-treated hydrocarbon to separate higher boiling componentstherefrom, and emulsifying remaining normally liquid olefin andlsobutane with concentrated sulfuric acid while maintaining the ratio ofisobutane to olefin at the point at which the olefin first contacts theacid between 50; 1 and 500: 1, whereby alkylation of the isobutane bysaid olefin is cited:- ed and polymerization is suppressed.

3. A process of producing higher boiling saturated hydrocarbons byalkylatlng an isoparaflin with an olefin which comprises contacting 9.normally liquid fraction of hydrocarbon cracking products containingsaid olefin with at least half its volume of a 55% to 70% solution of astron inorganic acid at between 80 C. and 50 C. for 1 to 15 minutes,distilling the acid-treated hydrocarbon to separate therefrom at leastthe higher boiling hydrocarbons formed by the acid treatment, andemulsifying remaining normally liquid olefin and said isoparafiin with aliquid acid alkylation catalyst under alkylating conditions.

acid-treated hydrocarbon to separate therefrom,

at least the diolefln polymerizationproducts, and emulsifying remainingnormally liquid olefin and said saturated tertiary hydrocarbon with aliquid acid alkylation catalyst under alkylating condi-' tions.

5. A process of producing higher boiling saturated hydrocarbons .byalkylating an isoparafiln with an olefin which comprises contacting anormally liquid fraction of hydrocarbon cracking products containingsaid olefin with a solution of an acid polymerization catalyst at atemperature at which polymerization of a part of the monoolefin contentof said fraction not greater than 5% of the total olefin content takesplace without substantial dilution of the acid solution, removing at"least the polymerization products from the acid-treated hydrocarbon,and emulsifying remaining normally liquid olefin and said isoparaffinwith a liquid acid alkylation catalyst under alkylating conditions.

6. A process of producing higher boiling saturated hydrocarbons byalkylating an aliphatic saturated hydrocarbon having a tertiary carbonatom with an olefin which comprises contacting hydrocarbon containing anormally liquid olefin and the corresponding diolefln with apolymerization catalyst to substantially polymerize'dlolefins togetherwith between 1% and 5% of the monoolefin content, removing p erizationproducts from the resulting hydrocarbon mixture, and emulsifyingremaining normally liquid olefin and said saturated tertiary hydrocarbonwith a liquid acid alkylation catalyst under alkylating conditions.

I. A process of producing higher boiling saturated hydrocarbons byalkylating an iso with a normally liquid mono-olefin which comprisescontacting said isoparaflin and olefin-with concentrated sulfuric acidunder alkylation conditions, separating used sulfuric acid from thereaction mixture, diluting a part of said separated I acid to aconcentration between 55% and 70% and contacting a fraction ofhydrocarbon crackingproducts containing said olefin with said dilutedacid at between 30" C. and 50 C. for 1 to 15 minutes while maintaining avolume ratio of acid phase to hydrocarbon of at least 0.5 to 1,neutralizing and distilling the acid treated hydrocarbon to separate afraction of substantially the same end point as the fraction treated andfeeding the separated fraction to said alkylation whereby the efiectivelife of the sulfuric acid catalyst is materially increased and the yieldand quality of the alkylation products are improved.

8. A process of producing higher boiling saturated hydrocarbons byalkylating an isoparaflin with a normally liquid mono-olefin whichcomprises contacting said isoparaifin and olefin with concentratedsulfuric acid under alkylation conaction mixture, contacting ahydrocarbon mixture comprising said olefin and a normally liquiddiolefin with a part of said separated used acid to substantiallypolymerize the diolefin content together with a minor amount of themono-olefin present, removing the polymerization products from the acidtreated hydrocarbon and feeding said hydrocarbon to said alkylationwhereby the 30 efiective life of the sulfuric acid catalyst ismaterially increased and the yield and quality of the alkylationproducts are improved.

9. A processor producing higher boiling saturated hydrocarbons byalkylating an aliphatic 5 saturated hydrocarbon having a tertiary carbonatom with a normally liquid olefin which comprises contacting a normallyliquid fraction of hydrocarbon cracking products containin said olefinwith used sulfuric acid from an alkylation 0 operation while maintainingpolymerization con ditions at which between about 1% and about 5% of themono-olefin content is polymerized, distilling the acid treatedhydrocarbon to separate polymerization products therefrom and emulsi-(lfying the polymer-free product and a molecular excess of saidaliphatic saturated hydrocarbon having a tertiary carbon atom withconcentrated sulfuric acid under alkylating conditions wherebythe'eflfective life of the sulfuric acid in said alkyl- 80 ation and theyield and quality of the alkylation.

' products are improved.

' SUMNER H. McALLISTER.

JOHN ANDERSON. WILLIAM E. ROSS.

ditions, separating used sulfuric acid from the re-

